Forklift with transverse travel system

ABSTRACT

A vehicle body ( 2 ) is provided with a pair of right and left front wheels ( 3 ) and a pair of right and left rear wheels ( 4 ), these wheels being adapted to be turned through 90 degrees. The front wheels ( 3 ) are attached to turning members ( 24 ) installed on the vehicle body ( 2 ) for turning around vertical axes ( 23 ), and turning means ( 40 ) are installed for turning the turning members ( 24 ). The front wheels ( 3 ) are operatively connected to travel drive means ( 30 ) respectively attached to the turning members ( 24 ). The travel drive means ( 30 ) extend rearward from the inner sides of the front wheels ( 3 ). Masts ( 6 ) are installed on the front end of the vehicle body ( 2 ), and forks ( 13 ) are installed on the masts ( 6 ). The front wheels are of the type in which they can be steered to turn sideways. And the travel drive means do not require the masts to be positioned more forwardly of the front wheels than necessary and the longitudinal balance can be satisfactorily maintained without increasing the self-weight.

TECHNICAL FIELD

This invention relates to a forklift having a transverse travel system,which can be switched to a transverse travel mode.

BACKGROUND OF THE INVENTION

Conventionally, vehicles having a transverse travel system have beenfound among large size conveyance vehicles and some loaders, and reachstyle electric vehicles as forklifts. In addition, there exists a sideforklift with a mast and forks installed sideways in relation to themovement direction of the vehicle to allow the vehicle to handleelongated objects. However, there are no counter balance type forkliftsthat can move sideways and function like a side forklift in addition tosuch tasks as generally required. To realize this type of forklift, thefront wheels or driving wheels are required to be steerable sideways.

Therefore, a conventional forklift 1, shown in FIG. 8, has a pair ofright and left front wheels 3 (driving wheels) in a front part of avehicle body 2, a pair of right and left rear wheels 4 (steerablewheels) in a rear part, and a driver's seat 5 on an upper front part ofthe vehicle body 2. A mast 6 capable of vertically extending andretracting is located at the front end of the vehicle body 2 to be ableto tilt in a front-and-rear direction through a front wheel axle 7extending in the vehicle width direction. Additionally, tilt cylinders 8enabling the mast 6 to tilt forward and backward are placed between thevehicle body 2 and the mast 6.

The mast 6 comprises a pair of right and left outer frames 9 and a pairof right and left inner frames 10 capable of vertical movement by beingguided by the outer frames 9. Disposed between the outer frames 9 andthe inner frames 10 is a lift cylinder 11. Additionally, lift brackets12 capable of vertical movement by being guided on the inner frames 10are provided, and a pair of right and left forks 13 are secured to thelift brackets 12 through a pair of upper and lower finger bars.

The above mentioned driver's seat 5 includes a seat 15, a steering wheel16 located in front of the seat 15, and a headguard 19 disposedthereabove through front pipes 17 and rear pipes 18 which are erected onthe vehicle body 2. Additionally, a counterweight 20 is located in therear of the seat 15 on the vehicle body 2.

However, since the right and left frontwheels 3 are driven in common bya same travel drive system, the above mentioned conventional forklift 1cannot effect straight-sideways steering of the front wheels, thus beingunable to move laterally.

BRIEF SUMMARY OF THE INVENTION

The present invention has an object to provide a forklift withtransverse travel system, in which front wheels and rear wheels can besteered straight sideways and the front-and-rear balance can bemaintained properly.

A forklift with transverse travel system in this invention comprises apair of right and left front wheels and a pair of right and leftrearwheels respectively mounted to a vehicle body to be steerable by 90degrees, the pair of right and left front wheels being connected toturning members capable of turning around vertical axes on the vehiclebody, and means for allowing the turning members to rotate, wherein thepair of right and left front wheels are respectively connected to traveldrive means attached to the turning members, these travel drive meansbeing provided to extend rearward from the inner sides of the frontwheels, and a mast is installed on the front end of the vehicle andforks are attached to this mast.

According to the above mentioned configuration, during normal travel,both the right and left front wheels and right and left rear wheels aresteered either forward or backward. In this condition, a lift lever isthen used to raise or lower the forks along the mast to accomplishexpected fork operations.

When changing from a normal travel operation to a transverse traveloperation, for example, a lever-style transverse travel mode switch isoperated to activated a turning means. Therefore, operating the turningmeans allows the front wheels to turn around the vertical axes, enablingsteering of the front wheels by 90 degrees (straight sideways) inrelation to the vehicle, thus the forklift can travel laterally to theright or the left after the front wheels are steered straight sideways.

Additionally, when the front wheels are steered straight sideways, thetravel drive means also turn integrally with the turning members andallow the inner width of portions of the travel drive means locatedalong the inner sides of the front wheels to move closer to the rearside of the mast. At the same time, the width of the inner sides of thetravel drive means, which extends from the inner faces of the portionslocated along the inner sides of the front wheels to the vertical axes,maybe formed narrow, so that projections extending forward from thevertical axes (or an interfering range with the mast) can be madenarrower (smaller) corresponding to the inner side width of the traveldrive means.

Consequently, in the system allowing the front wheels to steer straightsideways, it becomes unnecessary to install the mast so forward asunnecessary. That is to say, the mast may be installed in the samemanner as in a conventional non-laterally traveling forklifts, so thatthe front-and-rear balance of the forklift can be maintainedsatisfactorily without increasing the self-weight of the forklift.

In a preferred embodiment of a forklift with transverse travel systemaccording to the invention, in the configuration of the above mentionedclaim 1, each of the travel drive means comprises a revolution driveunit located in the rear of the front wheel and a revolutiontransmission unit located along the inner side of the front wheel totransmit the action of the revolution drive unit to the front wheel.

According to this preferred embodiment, because of the reasons that alarge shaped revolution drive unit can be positioned in the rear part ofthe front wheels and a thin type revolution transmission unit can bepositioned inside the front wheels, the inner width of the travel drivemeans which extends from the vertical axes to the inner sides of therevolution transmission units can be narrowed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic top view of a forklift with a transverse travelsystem according to an embodiment of the invention, emphasizing traveldrive means, (a) showing a normal travel time and (b) showing atransverse travel time;

FIG. 2 is a side view of the forklift with a transverse travel systemduring the normal travel time;

FIG. 3 is a side view of a front wheel portion of the forklift with atransverse travel system;

FIG. 4 is a partial cutaway front cross section of the front wheelportion of the forklift with a transverse travel system;

FIG. 5 is a partial cutaway top cross section of a rear wheel portion ofthe forklift with a transverse travel system;

FIG. 6 is a rear view of the rear wheel portion of the forklift with atransverse travel system;

FIG. 7 is a schematic top view emphasizing turning means of the forkliftwith a transverse travel system, (a) showing the normal traveling timeand (b) showing the transverse traveling time; and

FIG. 8 is a side view of a forklift of a conventional art.

PREFERRED EMBODIMENT

An embodiment of the present invention will be explained below usingFIGS. 1 through 7. In these embodiments, components identical or almostidentical to those of the conventional art (FIG. 8) are labeled withlike reference symbols and detailed explanations thereof are omitted.

Reference symbol 1 shows a forklift, 2 a vehicle body, 3 a front wheel(drive wheel), 4 a rear wheel (steerable wheel), 5 a driver's seat, 6 amast, 8 a tilt cylinder, 9 an outer frame, 10 an inner frame, 11 a liftcylinder, 12 a lift bracket, 13 a fork, 15 a seat, 16 a steering wheel,17 a front pipe, 18 a rear pipe, 19 a headguard, and 20 a counterweight.The mast 6 is installed on the vehicle body 2 to be able to swingforward or backward through a linking axle 28 in the direction of thewidth of the vehicle.

Each of the pair of right and left front wheels 3 are mounted to besteerable by 90 degrees (steerable straight sideways) in relation to thevehicle body 2. That is, turning members 24 are attached to the vehiclebody 2 to be able to turn around vertical axes 23 through bearings 21and vertical axes 22. These turning members 24 are inverted L-lettershaped and their horizontal plates are connected to the lower ends ofthe vertical axes 22. Axles 26 are installed sideways on the verticalplates through bearings 25 to be able to turn, and rims 3A of the frontwheels 3 are connected to these axles 26. The front wheels 3, at thistime, are configured to be positioned almost immediately under thevertical axes 23.

Each of a pair of right and left front wheels 3 are attached to theturning member 24, connecting to a travel drive means 30, and thistravel drive means 30 extends rearward from the inner sides of the frontwheels 3 toward the rear direction. That is, electric motors 31 (anexample of revolution drive unit) are located in the rear of the frontwheels 3 and are secured with its output axis 32 facing inward on theturning members 24 through brackets 33.

Also, inside of the front wheels 3, a chain transmitting mechanism (anexample of revolution transmission unit) 34 is placed to couple theoutput axis 32 of the electric motor 31 with the axle 26 of the frontwheel 3. This chain transmitting mechanism 34 is comprised of a drivingcogwheel 35 mounted on the output axis 32, a passive cogwheel 36 mountedon the axle 26, a chain 37 traveling between both cogwheels 35 and 36, acasing 38 and the like, and this casing 38 is secured to the turningmember 24.

Because these large sized electric motors 31 are disposed in the rear ofthe front wheels 3, and a thin type chain transmission mechanism 34 ispositioned inside of the front wheels 3, the inner width W of the traveldrive means extending from vertical axes 23 to the inner sides of thechain transmission mechanism 34 can thereby be narrowly formed.

A front wheel turning means 40 to allow the previously mentioned turningmembers 24 to turn is installed on the above mentioned vehicle body 2.That is, the front wheel turning means 40 is comprised of a front wheeltransverse travel cylinder 41 and this front wheel transverse travelcylinder 41 is mounted on the vehicle body 2 to allow its main body 41 ato be able to move up and down through a vertical pin 42, and a pistonrod 41 b is connected to a link 43 which is secured to one of theturning members 24 to be able to turn relatively through a connectingpin 44 in the vertical direction. In addition, all parts that areconfigured between the right and left turning members 24 and the arm 45are inter-connected and are able to turn relatively through a link 46and a connecting pin 47.

Consequently, by operating the front wheel transverse travel cylinder41, the turning member 24 is turned through the link 43, which enablesone of the front wheels 3 to steer straight sideways around the verticalaxis 23 and the other front wheel 3 to steer straight sideways aroundthe vertical axis 23 through arm 45, link 46, and the like. That is,according to the front wheel turning means 40, by the operation of thecommon front wheel transverse travel cylinder 41, the right and leftfront wheels 3 are configured to steer in different directions that isto be steered straight sideways. The above mentioned items 41 through 47and the like together form an example of the above mentioned front wheelturning means 40.

Each of a pair of right and left rear wheels 4 are mounted steerable by90 degrees (steerable straight sideways) in relation to the vehicle body2. That is, the pair of right and left rear wheels 4, with their rims 4Abeing mounted respectively on the vertical plate portion of the invertedL-letter shaped members 50 to be able to turn through an axle 51, andthe like in a horizontal direction, and such. The horizontal plates onthe turning members 50 are positioned to be able to turn around verticalaxes 54 on the vehicle body 2. The rear wheels 4 at this time areconfigured to position almost immediately under the vertical axes 54.

A rear wheel turning means 60 to allow the pair of right and left rearwheels 4 to turn around the vertical axes 54 is installed and this rearwheel turning means 60 is comprised of a steering cylinder 61, a rearwheel transverse travel cylinder 63 and the like.

This means that the steering cylinder 61 with its main body 61 a ispositioned in the direction of the vehicle width, and a piston rod 61 cconnected to the piston 61 b is protruding toward both sides in thedirection of the vehicle width. Both ends of the projection of thepiston rod 61 c are secured to the vehicle body 2 through a supportingframe 62, thus the main body 61 a is configured to be able to move inthe direction of vehicle width.

The rear wheel transverse travel cylinder 63 exists as a right and leftpair, and each of its main body 63 a is integrated (connected) to themain body 61 a of the previously mentioned steering cylinder 61 througha connecting member 64. At this time, each of the piston rods 63 cconnected to a piston 63 b of the rear wheel transverse travel cylinder63 is protruding outward in the direction of the vehicle width. Inaddition, an arm 65 is mounted on the upper end of the above mentionedvertical axis 53 and the protruding end of the piston rod 63 isconnected to turn relatively through a link 66, connecting pins 67,68,and the like in the vertical direction.

According to above mentioned rear wheel turning means 60, the operationof the steering cylinder 61 is conducted by moving the main body 61 atoward the secured piston rod 61 c in the direction of the vehiclewidth, and then, the main body 63 a of the rear wheel transverse travelcylinder 63 is moved integrally with the main body 61 a of the steeringcylinder 61 in the direction of the vehicle width. Meanwhile, inside thesupporting frame, a guide (not, depicted in the drawing) penetrating aconnecting member 64 is placed, and with this guide, the main bodies of61 a and 63 a are provided with both moving guidance and rotationprevention.

The operation of the above mentioned steering cylinder 61 is configuredto operate by an orbit roll (all hydraulic power steering) using thesteering wheel 16. Additionally, the rear wheel transverse travelcylinders 63 are configured as a right and left pair, and are able toturn the rear wheels 4 respectively by actuating a control valve whenthe steering cylinder 61 is in neutral, and when the steering cylinder61 is in operation, they are configured to be in a designatednon-operational posture.

Therefore, by operating the rear transverse travel cylinders 63, therear wheels 4 can be steered straight sideways with the vertical axes 53being turned through the links 66, the arms 65, and the like. That is,by the operation of the rear transverse travel cylinders 63, right andleft rear wheels 4 are configured to be steered in different directionsthat is steered straight sideways. By using the above mentioned 61through 71 and the like, an example of the rear wheel turning means 60will be able to turn a pair of right and left rear wheels 4 around thevertical axes 54 is configured.

A battery 75 is loaded on the above mentioned vehicle body 2, and acontroller 76 is attached to this battery 75. Additionally, cable (powersource supply part) 77 from this controller 76 is connected to each ofthe previously mentioned electric motors 31.

The following is an explanation of the operation of the above mentionedexample.

Indicated by the solid lines in FIGS. 1(a), 2 through 6, and 7(a) are anormal travel time. At this time, the right and left front wheels 3 andthe right and left rear wheels 4 are in the front-and-rear direction.The forklift 1 can be driven to travel by an operator sitting on theseat 15 of the driver's seat 5 by manipulating the steering wheel 16.

That is, the forklift 1 can move forward and backward by supplyingelectrical power from the battery 75 to the electric motors 31 by thecables 77 after controlling the electrical power with the controller 76,thereby to drive the front wheels in the front-and-rear directionthrough the chain transmission mechanism 34 and the like. Then, therevolution from the output axis 32 on the electric motor 31 can betransmitted to the front wheels 3 through the driving cogwheel 35, thechain 37, the passive cogwheel 36, and the axle 26.

Then, by operating a lifting lever to actuate the lift cylinders 11 toraise and or lower the forks 13 through the lift brackets 12 and thelike along the mast 6, the expected fork operations can be executed.Further, by operating a tilting lever to actuate the tilt cylinders 8 tomove the mast 6 around the linking axle 28 (that is to tilt), thepostures of the forks 13 can be varied through the lift brackets 12 andthe like.

During the traveling time mentioned previously, the steering isconducted by the manipulation of the steering wheel 16. Therefore, byturning the steering wheel 16 to the left side, the main body 61 a ofthe steering cylinder 61 is operated toward the left side by the orbitroll 70, and through the connecting member 64, the main body 63 a ofboth rear wheel traveling cylinders 63 is moved integrally to the leftside. In the meantime, both rear wheel transverse travel cylinders 63are playing a link-like role in the non-operational posture within thedesignated range of retraction. Therefore, the move of both of the rearwheel transverse travel cylinders 63 to the left side is transmitted tothe arms 65 through the links 66 to allow the turning members 50 to turnaround the vertical axes 54, and then to allow the rear wheels 4 tosteer to the left.

Further, when both of the rear wheel transverse-travel cylinders 63 areretracted half way, as indicated by the virtual lines in FIG. 1(a)describing right and left rear wheels 4, both turning members 50 areturned around the, vertical axes 54 in different directions to becapable of steering diagonally so that the outer edges are locatedslightly forward, thereby the steering becomes possible in thisposition. Additionally, in the same manner as described above, forexample, by turning the steering wheel 16 to the right, a right turn ispossible.

When changing from a normal travel operation to a transverse traveloperation, at first, the steering cylinder 61 is positioned in neutral(traveling straight forward) as shown in FIG. 5. With this condition,for example, a lever-style transverse travel mode switch (not depictedin the drawings) can be manipulated to actuate the front wheel turningmeans 40 and the rear wheel turning means 60.

That is, using the front wheel turning means 40, a lever styletransverse travel mode stitch can be operated, to tilt, thereby to movethe front transverse travel cylinder 41 which enables the turning member24 to turn around the vertical axis 23 through the link 43. Thus, asindicated by the virtual lines shown in FIGS. 1(b), 3 and 4, and theFIG. 7(b), the front wheels 3 are steered by 90 degrees(straight-sideways) in relation to the vehicle body 2. The travel drivemeans 30 then also is turned integrally with the turning members 24 andeach of the chain transmitting mechanism 34 is brought closer to therear side of the outer frames 9. Since the front wheels 3 are positionedalmost immediately under the vertical axis. 23, the front wheels 3 andthe like can be made compact and steerable by 90 degrees.

The rear wheel turning means 60 retracts both rear wheel transversetravel cylinders 63 by the control valve and then transmits theprojecting movement of the piston rod 63 c to the arms 65 through thelinks 66 for the turning members 50 to turn around the vertical axes 54,thus as indicated by the virtual lines of FIGS. 1(b) and 6, and by theFIG. 7(b), the rear wheels 4 can be steered by 90 degrees (straightsideways) in the relation to the vehicle body 2.

When the front wheels 3 and the rear wheels 4 are detected by a sensoras having changed the direction of travel or the front wheels 3 and therear wheels 4 have been steered straight sideways, an indicator lamp isactivated, thereby allowing the transverse travel mode to be affected.

Therefore, an operator of the forklift 1 sitting in the seat 15 of thedriver's seat 5 can operate the steering wheel 16, and as explainedabove, can supply the electrical power from the battery 75 after beingcontrolled by the controller 76 through the cables 77 to drive eachelectric motor 31, enabling the front wheels 3 to drive and turn in thefront-and-rear direction through the chain transmitting mechanism 34 andthe like to make the forklift 1 to travel laterally in either the rightor the left direction. The pair of right and left rear wheels 4 at thistime will follow the front wheels.

This transverse traveling capability will ease and facilitate, forexample, the transporting of elongated objects with the forks 13.Correction of straightness in the transverse travel can be easilyeffected by tilting the lever forward or backward to slightly actuatethe front wheel transverse travel cylinders 41 in order to allow forfine adjustment of the angle of the front wheels 3.

In the forklift 1 described above, this capability of forming a narrowinner width W of the travel drive means extending from the vertical axes23 to the inner sides of the chain transmitting mechanism 34 is enablingthe front wheels 3 to steer by 90 degrees in relation to the vehiclebody 2 using the front wheel turning means 40, and when the travel drivemeans 30 is turned integrally to bring the chain transmitting mechanismcloser to the rear side of the outer frames 9, the portion projectingforward from the vertical axis 23 (interfering range with the mast 6)becomes as narrow (small) as the previously mentioned inner width W ofthe travel drive means.

Because of this reason, although it is of a style that the front wheels3 can be steered straight sideways, the mast 6 does not have to bepositioned more forward than necessary in the relation to the frontwheels 3 and the like due to the travel drive means 30, therefore, themast 6 can be positioned in the same manners with the conventionalnon-lateral traveling forklifts. That is the reason that the balance offront and rear can be satisfactorily maintained without increasing theself-weight. Since the self-weight does not need to be increased, thissaves the wasteful consumption of the battery 75.

Although the forklift 1 of a counter balance type is shown in theembodiment above, this can also be applied to the side forklifts and thelike.

In the embodiment described above, the electric motors 31 are used as arevolution drive unit, however, this can also be hydraulic motors. Touse the hydraulic motors, as a drive style of the forklift 1, 2-pump2-motor type hydraulic drive system or 1-pump 2-motor type hydraulicdrive system can be used.

In the above mentioned embodiment, a style utilizing the common means,the front wheel turning means 40 will allow the pair of right and leftfront wheels 3 to turn simultaneously as shown, however, there can beanother style which can turn the pair of right and left front wheels 3each separately by its own independent front wheel turning means.

Although the type having the rear wheel turning means 60 capable ofrotating the pair of right and left rear wheels simultaneously is shownin the above mentioned embodiment, another style exists where one of therear wheels of the pair of rear wheels 4 may be of a type capable ofsteering by means of a steering wheel, while the other wheel is of afollow-up castor type. In this case, when switching to a transversetravel mode, one of the rear wheels 4 is forcedly steered by thecylinder or the like. A castor style may also be used for both rearwheels 4.

1. A forklift with a transverse travel system, comprising: a pair ofright and left front wheels and a pair of right and left rear wheelsrespectively mounted to a vehicle body to be steerable by 90 degrees,the pair of right and left front wheels being connected to turningmembers provided on the vehicle body to be turnable around verticalaxes; means for allowing the turning members to rotate; travel drivemeans installed in the turning members and connecting thereto the pairof right and left front wheels respectively, said travel drive meansbeing located to extend rearward from the inner sides of the frontwheels; a mast positioned on a front end of the vehicle body; and forksinstalled on the mast.
 2. The forklift with a transverse travel systemaccording to claim 1, wherein each of the travel drive means comprises arevolution drive unit located in the rear of the front wheel, and arevolution transmitting unit located on the inner side of the frontwheel to allow the revolution drive unit to be connected to the frontwheel.